SOLVED
We’ve solved our issue.
If the provided class is called by java directly, the Transformer factory com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl will be used. On Lucee oracle.xml.jaxp.JXTransformer. It looks like the transformer has some issues with the transormation. It’s possible to set a system property to choose the transformer explicitly.
System.setProperty("javax.xml.transform.TransformerFactory", "com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl");
Hint in the documentation:
The system property that determines which Factory implementation to create is named “javax.xml.transform.TransformerFactory”. This property names a concrete subclass of the TransformerFactory abstract class. If the property is not defined, a platform default is be used.
In this case, the transformation works fine.
Thanks for help!